In process control engineering, sensors are positioned in environments in order to measure their physical and/or chemical properties. In the area of the sensor, a measuring transducer is arranged, which transforms the sensor signal and processes it. The sensor and measuring transducer form a measuring chain, which in the following shall mean a transmission route of a primary sensor signal that depends on a parameter to be measured to a unit that is downstream of the sensor, wherein the downstream unit receives the sensor signal or an edited sensor signal in order to process it and to forward it in another form.
The measuring transducers are installed at the installation location and configured according to the measuring task and connected with a process control center. Disconnecting a sensor from a measuring transducer usually results in a fault signal in the process control center, unless a hold signal was initiated prior to intentionally disconnecting the sensor from the measuring transducer. However, manually initiating a hold signal at the measuring transducer is only possible if a direct control interface is provided locally on the measuring transducer. In case of measuring transducers that do not have such a direct control interface, informing the process control center about the intended action is mandatory in order to avoid a fault signal to be issued.